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Transforming growth factor beta1 attenuates ceramide-induced CPP32/Yama activation and apoptosis in human leukaemic
1Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan.
Abstract:
Ceramide, a product of sphingomyelin turnover, is a novel lipid second messenger that mediates important cellular functions including proliferation, differentiation and apoptosis. This study demonstrates that the CPP32/Yama protease was activated during apoptosis induced by the membrane-permeable second messenger C2-ceramide in HL-60 cells. We also found that the addition of a specific tetrapeptide inhibitor of CPP32/Yama, Ac-DEVD-CHO, provided an effective protection against ceramide-induced cell death. These results suggested that CPP32/Yama has a central role in ceramide-mediated apoptosis. Furthermore a wide variety of cytokines were examined for their effect on ceramide-induced apoptosis. Only transforming growth factor beta1 (TGF-beta1) (1 ng/ml) exerted significant prevention of apoptosis induced by C2-ceramide, or by sphingomyelinase (increases intracellular ceramide). Consistently, TGF-beta1 abrogated the cleavage of poly(ADP-ribose) polymerase and the production of the CPP32/Yama active subunit, p17. However, TGF-beta1 treatment did not cause growth inhibition or alter the level of cyclin-dependent kinase inhibitor p27. It suggests that the preventive effect of TGF-beta1 is not mediated by growth arrest. Interestingly, we found that TGF-beta1 prevented the C2-ceramide-caused decrease of Bcl-2 protein. We thus propose that TGF-beta1 rescues ceramide-induced cell death, possibly by maintaining the constant level of Bcl-2, thereby abolishing CPP32/Yama protease activation.
Insights
Ceramide triggers apoptosis by activating the CPP32/Yama protease. Transforming growth factor beta1 (TGF-beta1) prevents this cell death by maintaining Bcl-2 protein levels, thus inhibiting protease activation.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Ceramide is a lipid second messenger regulating cell proliferation, differentiation, and apoptosis.
- Sphingomyelin turnover generates ceramide, influencing cellular signaling pathways.
- Understanding ceramide's role in apoptosis is crucial for cellular regulation research.
Purpose of the Study:
- To investigate the role of CPP32/Yama protease in ceramide-induced apoptosis.
- To identify cytokines that modulate ceramide-induced apoptosis.
- To elucidate the mechanism by which TGF-beta1 affects ceramide-induced cell death.
Main Methods:
- Induction of apoptosis in HL-60 cells using C2-ceramide and sphingomyelinase.
- Assessment of CPP32/Yama protease activation and poly(ADP-ribose) polymerase cleavage.
- Treatment with TGF-beta1 and a CPP32/Yama inhibitor (Ac-DEVD-CHO).
- Analysis of Bcl-2 protein levels and cyclin-dependent kinase inhibitor p27.
Main Results:
- CPP32/Yama protease activation was observed during C2-ceramide-induced apoptosis.
- Inhibition of CPP32/Yama protease protected cells from ceramide-induced death.
- TGF-beta1 significantly prevented apoptosis induced by C2-ceramide or sphingomyelinase.
- TGF-beta1 abrogated CPP32/Yama activation and poly(ADP-ribose) polymerase cleavage.
- TGF-beta1 prevented the decrease in Bcl-2 protein levels caused by C2-ceramide.
Conclusions:
- CPP32/Yama protease plays a key role in ceramide-mediated apoptosis.
- TGF-beta1 acts as a protective agent against ceramide-induced cell death.
- TGF-beta1 likely rescues cells from apoptosis by preserving Bcl-2 protein levels and inhibiting CPP32/Yama activation, independent of growth arrest.